U.S. Pat. No. 4,337,182, incorporated by reference herein, describes a poly(arylene sulfide) composition suitable for encapsulating semi-conductors. The composition disclosed in that patent includes a small amount (about 0.5 to 3 weight percent) of an organic silane. The purpose of the organic silane, as taught by the patent, is to function as a coupling agent, to impart improved water resistance and to decrease the linear coefficient of expansion of the composition. The only organic silane species specifically identified are:
gamma-glycidoxypropyltrimethoxysilane PA1 methyltrimethoxysilane PA1 polyisoxymethoxysilane PA1 vinyltris(2-methoxyethoxy)silane PA1 beta-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane PA1 N-beta(N-vinylbenzylamine)ethyl gamma-aminopropyltrimethoxysilane monohydrogen chloride PA1 (a) poly(phenylene sulfide), PA1 (b) fiber glass, PA1 (c) talc or silica, and PA1 (d) N-{2-[3-(trimethoxysilyl)propylamino]ethyl}-p-vinylbenzylammonium chloride.
The patent further teaches that the last of these silanes is preferred. Another name for this preferred silane is N-{2-[3-(trimethoxysilyl)propylamino]ethyl}-p-vinylbenzylammonium chloride.
The Phillips Chemical Company (a division of Phillips Petroleum Company, Bartlesville, Okla.) has marketed an encapsulating composition containing this silane. The composition comprises:
Electronic components are coated or encapsulated with this poly(phenylene sulfide) composition to maintain electrical insulation, to provide mechanical protection and to otherwise shield the component from exposure to its environment.
One very important property of any encapsulation material is electrical resistance. In use, the encapsulation material is generally subjected to a hostile environment that adversely affects the desired properties of the material. Of particular concern are the effects of high temperature conditions and/or of high humidity conditions. Such conditions can cause a decrease in the electrical resistance of the encapsulation material.
It is an objective of those of skill in the art of poly(arylene sulfide) encapsulation compositions to produce compositions which retain high electrical resistance when subjected to hostile conditions such as, for example, high temperature and high humidity. It is also an objective of those of skill in this art to produce poly(arylene sulfide) compositions of increased electrical resistance.
Another objective of those of skill in the art is to produce poly(arylene sulfide) compositions of decreased specific conductivity.